Nothing; the end of the ancient fiddlesticks ending in a point; hence metaphorically used to express a thing terminating in nothing.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
fiddle faddle * fidgetsNathan Bailey's 1721 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes